1. Field of the Invention
This invention relates to a double row ball bearing, and more particularly to a double row ball bearing (called a tandem type) which can suitably support a pinion shaft, for example, of a final reduction gear of an automobile, and is lubricated by lubricating oil received within the final reduction gear.
2. Related Art
Tandem type double row ball bearings which include a plurality of balls arranged in two rows between an outer ring and an inner ring, and a cage holding these balls have been extensively used in a pinion shaft support apparatus for a vehicle, etc., as shown in JP-A-2006-234100.
FIG. 3 shows a differential gear device which is one example of apparatus in which a double row ball bearing of the present invention can be used. The differential gear includes a pinion shaft 42 rotatably supported on a housing 41 and having a pinion gear 43 provided at a rear end thereof, a ring gear 44 meshing with the pinion gear 43, a pair of inner and outer double row ball bearings 45 and 46 rotatably supporting the pinion shaft 42 on the housing 41, and a drive shaft-connecting flange coupling 47 formed at an outer end of the pinion shaft 42.
In this differential gear, lubricating oil splashed up in accordance with the rotation of the ring gear 44 flows through a lubricating oil passageway 48 within the housing 41, and is introduced into a region between the pair of double row ball bearings 45 and 46. With respect to a supporting structure of the pinion shaft 43 and with respect to an oil supply from the oil passageway 48, one 45 of the double row ball bearings is located on a side of the pinion gear 43, while the other 46 of the double row ball bearings is located on a side opposite to the pinion gear 43. When the double row ball bearings 45 and 46 rotate, a flow of the fluid (a pumping action) from a smaller-diameter side of each bearing toward a larger-diameter side thereof occurs. Therefore, the double row ball bearings 45 and 46 used in the differential gear device are arranged such that their smaller-diameter sides are opposed to each other in an axial direction, and the lubricating oil is supplied from the smaller-diameter side of each bearing (that is, from the region between the pair of double row ball bearings 45 and 46) and is discharged from the larger-diameter side, utilizing this pumping action. This lubricating method is commonly used.
In a pinion shaft support apparatus of a vehicle, etc., to reduce a running torque of a bearing in order to achieve a low-loss design has been a problem. For reducing the running torque, it is effective to suppress an oil agitation loss caused by the lubricating oil.